(A) Fay and Lankhelma, in J. Am. Chem. Soc., 74, 4933-5 (1952), disclose the reaction of cyclohexene and phosphorus pentasulfide to produce .DELTA..sup.2 -cyclohexenylthionophosphine sulfide, which they propose exists as the dimer having the formula ##STR2##
(B) H. Z. Lecher et al., in J. Am. Chem. Soc., 78, 5018-22 (1956), disclose the reaction of phosphorus pentasulfide with benzene, o-xylene, anisole, phenetole, naphthalene and 2-isopropylnaphthalene to form the corresponding dimeric arylthionophosphine sulfides. They are, however, skeptical of the four-membered ring structure proposed by Fay and Lankelma, which would be unique among phosphorus compounds, and suggest that the electrostatic attraction between semi-polar P.fwdarw.S bonds causes a bimolecular association in solution, i.e. that the compounds have the following formula ##STR3## in which Ar is phenyl, o-xylyl, p-methoxyphenyl, p-ethoxyphenyl, 2-naphthyl or 2-isopropyl-X-naphthyl. They state that the very low solubility of these arylthionophosphine sulfides in organic solvents at room temperature also suggests their polar nature. However, regardless of the exact structure, this publication teaches the preparation of two compounds which are closely related to the compounds of Formula II of the present invention, i.e. compounds of Formula II in which R.sup.1 is methyl and ethyl rather than a straight or branched chain alkyl group having from four to six carbon atoms, as described and claimed herein.
(C) H. S. Pedersen et al., in Bull. Soc. Chim. Belg., 87, 223-228 (1978), describe the conversion of various ketones, such as benzophenone, 2-benzoylthiophene, dicyclopropyl ketone and camphor, to the corresponding thioketones, using the dimer of p-methoxyphenylthionophosphine sulfide of the formula ##STR4## as the thiation reagent. The reaction is conducted in anhydrous toluene at 110.degree. C. until all ketone is consumed (as shown by TLC).
(D) S. Scheibye et al., in Bull. Soc. Chim. Belg., 87, 229-238 (1978), describe the use of the dimer of p-methoxyphenylthionophosphine sulfide as a thiation reagent for converting a representative series of aliphatic and aromatic primary, secondary and tertiary carboxamides to the corresponding thiocarboxamides. They point out that the thiation reagent is quite insoluble in most solvents except in hexamethylphosphoramide (HMPA) at elevated temperatures. Thus, all reactions were conducted in HMPA in the temperature range of 80.degree.-100.degree. C.
(E) S. Scheibye et al., in Bull. Soc. Chim. Belg., 87, 299-306 (1978), describe the use of the dimer of p-methoxyphenylthionophosphine sulfide as a thiation reagent for conversion of secondary o-hydroxybenzamides of the formula ##STR5## in which R is phenyl, 2,6-dimethylphenyl, benzyl, n-hexyl or cyclohexyl, to the corresponding thioamide. Because of the insolubility of the thiation reagent in most solvents, the reactions were conducted in HMPA, initially at 140.degree. C. and then lowered within 30 minutes to a temperature in the range of 100.degree.-120.degree. C. Yields of desired product were in the range of 15-51%. With the exception of the cyclohexyl compound, where only the desired product was obtained (36%), the reaction gave side products of the formulae ##STR6## in yields of 5-24% and 13-21%, respectively.
(F) H. Fritz et al., in Bull. Soc. Chim. Belg., 87, 525-534 (1978), describe the use of the dimer of p-methoxyphenylthionophosphine sulfide for the conversion of various N,N-dialkylamides, e.g. those of the formulae ##STR7## wherein the alkyl groups contain from 1 to 12 carbon atoms and R is hydrogen, methyl, ethyl, propyl, trifluoromethyl, etc., to the corresponding thioamide. The thiation reactions were conducted in anhydrous toluene at a temperature of 100.degree. C.